<!DOCTYPE html>
<html lang="en-US">
<head>
</head>
<body>
  <x-foo></x-foo>
  <script>
    var prototype = Object.create(HTMLElement.prototype);
    prototype.createdCallback = function() {
      createdCallbackCalled = true;
    }
    document.registerElement('x-foo', {prototype: prototype});
  </script>
</body>
</html>
